1. Field of Invention
The present invention relates to a method for diagnosing efficiency of a low pressure exhaust gas recirculation (EGR) system and a low pressure EGR cooler. More particularly, the present invention relates to a temperature calculation method for a low pressure EGR cooler of a low pressure EGR system and a low pressure EGR cooler efficiency diagnosis method, which uses a low pressure EGR valve model and a low pressure EGR cooler model.
2. Description of Related Art
Generally, most diesel engines are provided with an exhaust gas recirculation (EGR) system so as to satisfy exhaust gas regulations.
The exhaust gas recirculation system recirculates a part of the exhaust gas exhausted from the engine to an intake line to reduce the combustion temperature of the engine and to reduce the NOx generation amount.
NOx elimination has become an important factor pursuant to the exhaust gas regulations of the EU and North America, and a low pressure EGR system as well as a high pressure EGR system are used so as to efficiently control the temperature and the flow rate of the recirculated exhaust gas.
Particularly, an EGR cooler has been recently applied to meet the exhaust gas regulations for the diesel engines. However, since the EGR cooler cools the exhaust gas, smoke or particulate matters (PM) may block the inner passage of the EGR cooler. In this case, the efficiency of the EGR cooler is deteriorated.
When the efficiency of the EGR cooler is deteriorated, the exhaust gas is not normally cooled and it is hard to know whether the EGR cooler is blocked or not by appearance, and therefore it is necessary to develop a model or method to predict the efficiency of the cooler. More particularly, it is necessary to check the efficiency of the EGR cooler without disassembling the EGR cooler.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.